Assiguos to timitjs olseet



Dec. 4, E928.

R. B. LEWES MECHANISM FOR PREVENTING LOST MOTION Filed Jan. 26, 1928 INVENTOR: Fafif/B Zen 51s,

ATTORNEY.

Patented l, 12.118,

TESTING MACHINE COMPANY, OF EIxlILi-MDELJHHL PEN T1011 OF PENNSYLVANIA.

LISFZ'LVAETIA, A CORPORA- MECHANISE/i FOE EREVE'NTING- LQEST IJIGTION.

Application filed January 36, 1928.

The present invention rel tes to a device for automat cally con'ipensatn r for wear be tween two ins anical parts aid the accurate transniitt-ingi of motion from one part to another.

in the various arts and more particularly in indication devices, such testing); instruments and many otl'ier machines and apparatus, lost motion, due to wear and other cruises introduces an element of error which prevents true and accurate readings being obtained. Some of the ol j: ts o the present invention are to provide a device whereby t he motion of a part can be ransmitted without loss; to provide a iuechanini of simple yet eiiicient construction for eliminating lost motion; to provide a device operable in one term thereof as control for the pointer of an indicating instrument whereby a given movement causes the pointer to assume a position exactly corresponding to this translated movement to furnish an. accurate reading; upon a scale; to provide a device for automatically overcoming the errors caused by lost motion; and to provide other improvements will hereinafter appear.

In the accompanying drzm'inos 1 represents a perspective ot a device embodying one form of the present invention; and Fig. 2 represents a section on line 2-2 of Fig. 1.

Referring to the drawings, one Form of the present invention is shown applied to the operation of a pointer 10 of an indioaton which, in the present insta ice, is employed as measure of: the movement transmitted. The pointer 10 is fast to a spindle 11 which carries a pinion 12 fast thereon for the purpose of transmitting movement thereto and thence to the pointer 10.

In order to cause the pinion 12 to turn, it is mounted in mesh with a rack 13 which is tree to slide in fixed quides 14 and has one end rigidly connected to bar opposite end of the rack 13 is tree to move in the guides 14 and receives its motion. by movement of the bar 15', and it is the movenlent ot the latter which it is here sought to measure through the medium of the pointer 10 operatinp; in, conjunction with dial 116 graduated in suitable units. It will be evident that while the pinion 12 and rack .13 are accurately fitted, the movement of one will be truly transmitted to the other, but where wear has Serial No. 249,571

taken place and there is a lost motion between the two parts an element of error is introduced so that the reading of the pointer 10 is not a true and accurate reading of the amount 0;? movement oi the bar 15.

For the purpose or preventir error due to lost motion, the pinion 12 is also in mesh with a second rack 11' which is arranged in substantially side to side abutting relation with the rack 13 but is free to move relative to the aforesaid rack Thus, in this instance, the rack bar 17 is provided with slots 1 which respectively receive pins 20 fast to and projecting from the side of the rack 13. This slotted pin construction maintains the rack bar 17 in proper operative alignment with the bar 13 while a spring 21 is sh'etched between a hip; 22 of the rack bar 17 and the bar 15. Since the ack bar 17 is also freely slidable in the guides 14 and is constantly pulled by the spring 21 toward the bar 15, it will be evident that one tooth of the pinion 12 will be pressed at one side by a tooth of the spring pressed rack 17 while its opposite side will be pressed against a tooth oi the rack 13. in this way, wear between the racir teeth parts and the pinion teeth is automatically compensated and no lost motion can possibly take place.

lln the operation of the present device, it will be assumed that the motion to be measured. is transmitted to the bar 15 so that it moves to the left as seen in 1. This movement also draws the rack 13 to the left, and at once the spring 21 causes the rack 1'? to move in the same direction maintaining its pressure against the teeth of the pinion so that the latter rotates a distance which represents an accurate measure of the movement transmitted to the bar 15, and as the pointer 10 is correspondingly rotated it will assume position upon the indicating dial so that a reading; can be taken as a measure of the movement;

From the foregoinc; it will. now be apparent that a complete unitary device has been devised whereby motion of a part can be accurately measured and indicated without the introduction an error due to lost motion and which is accurate irrespective of the direction of movement of a part, the motion of which is to he measured. Furthermore, since the motion transmitting parts are maintained constantly pressing against a pinion, there is no chance of wear becoming a factor in the resulting indication.

Having thus described my invention, I claim:

1. In a device of the character stated, the combination of a pinion, a rack in mesh with said pinion, a second rack in mesh with said pinion and mounted for relative movement with respect to said first rack guides for respectively supporting said racks, a bar connected to one end of said first rack, and a spring; stretched between said bar and said second rack whereby lost motion between said pinion and racks is prevented.

2. In a device of the character stated, aindicating pointer, means includi a pinion for operating said pointer, a racn in mesh with said pinion, a second rack also in mesh with said pinion and mounted for movement relative to said first rack, guides for the re spective racks, a bar connected to one end of said first rack and a spring stretched between said bar and said second rack whereby lost motion is prevented and said pointer indicates the exact movement oi? saia'l firs Signed at Philadelphia, count-v d iia State of Penns lvania t iis 25th da 101 1 7 J 7 oi January, 1928. V

ROBEfiT i5. LE WIS. 

